Bob Latham wrote:
I may be wrong but I thought all transmitters that broadcast com7 and com8
now were using C56 and C56 as a national SFN. Certainly Sutton Coldfield
is.

At Waltham, COM5 and COM8 swapped places last month, so that COM8 is on
ch56, but COM7 is still on ch31, presumably it will swap places with
COM6 to ch57 at some point, but I think there are no further changes at
Waltham until 2020?